A 3D heteropolyoxoniobate framework based on heart-shaped {Te 2 Nb 19 O 60 } clusters with proton conductivity property.

A 3D tellurium-substituted heteropolyoxoniobate framework H 5 K 3 Na[Cu(en) 2 ] 2 [Cu(en) 0.75 (H 2 O) 2.5 ]{[(Te 2 Nb 19 O 58 )(μ 3 -OH) 2 ]}·24H 2 O (1, en = ethylenediamine) with a 6-connected pcu topology is built from heart-shaped {Te 2 Nb 19 O 60 } clusters and copper complexes. The {Te 2 Nb 19 O 60 } cluster represents the new tellurniobate structure type with a 19-nuclearity Nb cluster. It consists of two new monovacant Lindqvist {Nb 5 O 19 } clusters, one boat-shaped {Nb 9 O 32 } cluster and two TeO 3 2- anions. The {Te 2 Nb 19 O 60 } polyanions are interlinked by [Cu(en) 2 ] 2+ complexes into a 2D (4, 4) grid-like layer containing rhombic sheets. The Cu 2+ supports the adjacent layers through Te-O-Cu-O-Te- bonds to form a three-dimensional heteropolyoxoniobate framework with 1D channels. This compound exhibits good chemical and solvent stability and proton conductivity, with a conductivity of 7.9 × 10 -3 S cm -1 at 85 °C under 98% RH.